Seoul, South Korea — US nuclear envoy Christopher Hill this week is making what may be the final effort of his search for a lasting deal on North Korea's nuclear program in the latest round of six-party talks in Beijing.

No one, including Mr. Hill, predicts success as he attempts to get North Korea to agree in writing to what North Korean diplomats have said they will never do: permit inspectors to take material from the North's nuclear site at Yongbyon for scrutiny outside the country.

Hill, entering the talks on Monday, acknowledged negotiations will be "difficult" but insisted, "We all know what we're supposed to get accomplished."

That word has come up repeatedly of late with Hill saying North Korea verbally agreed in October to allow sampling before President Bush ordered removal of North Korea from the US list of nations sponsoring terrorism.

Hill sought an understanding with Mr. Kim in Singapore last weekend, but Kim said, "we need more discussions."

Analysts say North Korea is hoping that Mr. Obama will send a high-level envoy to North Korea – a gesture of respect that might encourage progress.

Paik Hak-soon, director of North Korean studies at the Sejong Institute, says hard-liners in Washington are responsible for raising the issue of "sampling," which he says did not come up before October.

As for Hill's current mission, Lee Jong- min, dean of international studies at Yonsei University, says "chances are slim to none" for a last-minute breakthrough.

He believes North Korea's refusal to deal with Japan at this week's talks may alone make a deal impossible.

"They've thrown a monkey wrench," says Mr. Lee, calling North Korea's rejection of Japan a device "to deflect responsibility" for the failure of the talks.

North Korea's ostensible reason for refusing to talk to Japan is Japan's refusal to join the other negotiating partners – China, the US, Russia, and South Korea – in sending oil or other energy aid promised in tandem with disablement of the North's nuclear facilities at Yongbyon.

Japan says North Korea must account for all the Japanese believed to have been kidnapped from Japan more than 25 years ago, not just the 13 already acknowledged. North Korea says there are no more.

Frustration in the talks parallels mounting difficulties between North and South Korea, climaxed by North Korea's sharply curtailing access to the Kaesong economic complex about 40 miles north of Seoul.

North Korea hasn't halted operations at the complex's 88 factories, which employ 36,000 North Koreans, but has cut the number of South Korean managers and technicians with access to the zone from 1,600 to 800. North Korea has also curtailed truck traffic, reducing sales by 20 percent, say South Korean executives.

Yoo Chang-keun, vice chairman of the complex and president of a factory, says "no political agenda" need be linked to the complex.

He blames denial of access on a campaign by North Korean defectors to shower the North with leaflets dropped from balloons launched just below the demilitarized zone. Under government pressure, one group suspended drops. Another, the Christian Defectors Association, hasn't.

Lee Min-bok, a North Korean defector, calls the leaflet drops "psychological warfare" and cites North Korean rage as proof of hitting their targets.

"The North Korean soldiers are gathering the leaflets," says retired Army col. Choi Hyo-wan. "That means the North Korean people are picking them up."